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General How rare are 1g EPROM ECUs?

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TsiTuner

20+ Year Contributor
88
0
Dec 17, 2001
Somewhere, Louisiana
I heard in the past that all 1gs came with an EPROM ECU but this can't be true. This is the 3rd 91 AWD DSM I've owned and the first one that came from the factory with an EPROM, needless to say I was excited. :rocks:

I opened up the ECU today to check because I plan to order DSMLink in the next couple of months while I'm working on her. So how rare are the EPROM ECUs?
 
I've owned a few DSMs and never had a EPROM one, quite rare but there out there in cars here and there.
 
I have a few laying around. I think it's about a 50/50 shot
 
I thought something was strange about this car because on the area by the stick shift there is a button that says "eco/pwr". Neither of the other 2 cars had that button which made me think I may have gotten an EPROM this time
 
From what I've seen and heard people quote from looking at Mitsubishi production all 90's have em, most of 91, some of 92 and hardly any in 94. Why this is IDK, you think it would be reversed.

I thought something was strange about this car because on the area by the stick shift there is a button that says "eco/pwr". Neither of the other 2 cars had that button which made me think i may have gotten an eprom this time

That must be a five speed swapped car. That's for the other map on the TCU (full line pressure and higher shifts)
 
From what I've seen and heard people quote from looking at Mitsubishi production all 90's have em, most of 91, some of 92 and hardly any in 94. Why this is idk you think it would be reversed.



That must be a five speed swapped car....that's for the other map on the TCU (full line pressure and higher shifts)

No not all 90s came with them it's hit or miss on them as well. I've owned two 90s neither had one, but I found one in a 90 at the junkyard.
 
No its not a 5 speed swapped car. I ran the VIN before i purchased it and it shows up as an AWD manual vehicle
 
Well, somehow somebody put an auto econ mode button in the place of the coin holder.

I think the EPROM works out to about 10% of the cars. I have went though about 80 -90 turbo 1G cars and have probably got 9 to 10 EPROM ECU's out of them. Most of the auto turbo cars I have had did have an EPROM. Seems like the 5 or 6 auto AWD cars I have had they were all EPROMs. They are not rare but are kind of hard to find sometimes.
 
When you need one, they are as rare as a unicorn. When you have two and only one car, others seem to flock to you and pile up in your garage.
 
Both of my 1G's, one FWD and one AWD, came to me with EPROMS installed. Of course neither of these cars have sunroofs, too....which is quite a rare find as well.

Though with ECMTuning now having the ability to convert non-EPROM ECU's and the fact that chip tuning is basically on it's way out, they're not quite as valuable as they once were so more of them are becoming "available" and at better prices.
 
Removing your EPROM chip, reburning it with whatever your settings would be, and either reinstalling it as-is or running it with a piggyback device like an AFC.

It's the main reason companies like DSMchips.com are no longer in business- ECMLink, Ostrich, and other tuning solutions are too affordable, easy-to-use, and hands-down better these days.
 
I plan to order link in the next couple of months while im working on her.

You know it's not a plug and play deal right? The factory EPROM chip is actually soldered to the board, and must be removed and replaced with a socket before it is ready for another chip of any kind. Based on some of the questions you were asking, I just wanted to make sure you are aware of this. Good luck with the build.
 
Ive owned several DSMs and I have never seen a EPROM ECU in any of mine, with that since I run DSMLink I had ECMTuning just convert mine.
 
My 1990 1g AWD talon came with an EPROM ECU, not all 90's had the EPROM I physically have 3 extra ECU's in my garage, one is out of a 1991 turbo FWD auto transmission Eclipse, and it had the EPROM. The other two came out of 1990 turbo Eclipses one of which was an AWD model, and both of them were not EPROM equipped.

I do know from experience, that the earlier 1989-1990 is more common to find the EPROM on compared to the 1991-1994, you sometimes get lucky.
 
Back in the late 80's and early 90's, automotive microprocessor chips were either mask programmed ROM (they make the transistors for the ones and zeros of the software at the same time as they are making the ones for the processor gates) or fuse based ROM. Once you had good software, including the EPA approved fuel and timing maps you could send the software bits to the microprocessor factory and they would start making MPU chips, and 8 to 12 weeks later you would see parts and if everything was good you could start making ECUs with them.

Since the production line couldn't something like wait 8-12 weeks for custom CPUs the factory would the same ECU design as the development teams used with a interface circuit that could run the software from an external chip (the EPROM) that they could program over and over or in bulk and ship cars. The downside was those ECUs were at least $10 more in just raw parts and may have been several hundred $ more each actual cost. If you making a couple hundred thousand cars that's some real money, so as soon as you can you switch to the cheaper masked programmed MPU part and stop shipping EPROM ECUs. So typically you would see the EPROM ECUs in the early production months and then from time to time as the Just in Time delivery process failed and they needed ECUs to keep the production line running.

It wasn't until 98 or so that the ECUs started getting flash memory (a type of EEPROM) inside the processors allowing the factory and their service arms to update the programming at the plant or in the field.

For cars like the GVR4 there wasn't enough volume to justify a custom masked programed part so all the cars received EPROM ECU's but DSM production levels were such than no year had only EPROM ECUs
 
Both of my 1G's, one FWD and one AWD, came to me with EPROMS installed. Of course neither of these cars have sunroofs, too....which is quite a rare find as well.

Though with ECMTuning now having the ability to convert non-EPROM ECU's and the fact that chip tuning is basically on it's way out, they're not quite as valuable as they once were so more of them are becoming "available" and at better prices.

Ha, I'm glad you corrected this two posts down. I was going to say have you been on my forum (dsmecu.com) where chip tuning is very much alive? :D

I really think paying the DSMLink guys to turn non eprom computers into tuneable ones is a good idea. There are probably a ton of ecu's out of other mitsus that will work for this as well. If I ever ditch my ostrich (likely never ever going to happen) then I'll be getting some sort of standalone computer.

I also have 2x 2g eprom ecu's on the shelf that I plan to socket and try out since I have the bin/xdf's for a 2g.
 
To answer the original question, I will estimate the ratio at 40/60 (eprom/non-eprom). Earlier cars seem to have more eproms. Not a scientific number, but what think it is, after looking at 50-60 cars over the 19+ years ;).

I really think paying the DSMLink guys to turn non eprom computers into tuneable ones is a good idea. There are probably a ton of ecu's out of other mitsus that will work for this as well. If I ever ditch my ostrich (likely never ever going to happen) then I'll be getting some sort of standalone computer.

Eprom ECUs used to be more valuable ($50-100 vs $200-$250), but with ECMTuning charging $90 to convert to eprom vs $30-40 to install the eprom socket, the difference is pretty much gone (certainly should not be more that $50). So I wouldn't sweat it ;)
 
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